In many applications where two or more apparatuses may share or communicate data with each other. In some applications, it is desirable to be able to very accurately synchronize the data to a common sense of time that is shared among the apparatuses. Synchronization becomes a necessity, for example, when apparatuses working at a significant distance from each other must also work in conjunction with each other.
As an example, FIG. 1 illustrates an example of a test system 10 comprising a plurality of test instruments 2 in communication with each other over a communication channel 4. In some embodiments, communication channel 4 may operate in accordance with a set of standard protocols, for example Ethernet or LAN eXtensions for Instrumentation (LXI). In some embodiments, communication channel 4 may include the Internet. One or more of test instruments 2 may be configured to receive and/or transmit data from, or to, one or more devices 6, for example devices under test (DUTs).
In the example test system 10, test instruments 2 work in conjunction with each other to test and/or measure data or parameters of one or more devices 6 which, in some cases may belong to a larger system or network. Furthermore, test instruments 2 may be separated from each other by significant distances, such that in some embodiments no common reference clock is distributed to the test instruments 2 via communication channel 4.
Accordingly, it may be necessary to synchronize data that is gathered, processed and/or processed by the test instruments 2 such that the test instruments 2 can work in conjunction to process the data appropriately. A test instrument 2 may include an internal clock which sets a timing by which data is sampled and processed within the test instrument. 2. To synchronize data operations among a plurality of test instruments 2 in a test system 10, the clocks of all of the test instruments 2 may be set to the same frequency, or to have a known frequency relationship with respect to each other.
However, even if two clocks are designed identically and set to operate at the same frequency, there is no guarantee that they will stay in synchronization. Several factors can cause two identical clocks to drift in frequency with respect to each other. Factors such as differences in manufacturing tolerances, differences in operating temperature or voltage, and the age of the clocks themselves can all affect the quality of synchronization. As a result, the clocks may drift with respect to each other such that when viewed over a long enough period of time they are not operating at the same frequency. As a result, over a long enough period of time, data sampled and processed by test instruments 2 will not remain synchronized.
Accordingly, it would be desirable to provide a method and system for synchronizing data that may be shared among two or more apparatuses that each operate with their own clock. It would also be desirable to provide a method and system for synchronizing data sampled with an internal clock, to an externally supplied reference timing signal, and particularly an externally supplied timing signal that provides absolute time information.